Electronic devices, particularly consumer electronics, must interact with users of the devices by means for receiving input from the user and means for providing output to the user. Classical forms of input include keyboard and mouse devices, but also include newer touch screen devices. Classical forms of output include digital displays and toggle lights, but also include newer liquid crystal display (LCD) technology.
Another form of output that many electronic devices provide is haptic feedback. For example, many smartphones include a rotating mass motor that vibrates when users touch the screen or to indicate a notification of new email or incoming call. However, this haptic feedback is extremely limited and is not localized to any particular part of the smartphone. Further, the motor is a large physical object that restricts smartphone design and limits the ability of designers to reduce the thickness and other dimensions of the smartphone. Additionally, the motor consumes significant power in comparison to the capability provided by the motor, particularly in comparison to the thin-film semiconductor-based components within the smartphone.
Many of these same electronic devices rely on tactile sensing for receiving input from the user. One conventional tactile sensing technology is illustrated in FIG. 1. FIG. 1 is a conventional smartphone with capacitive touchscreen. A smartphone 100 may include a rotating mass motor 110 for providing the haptic feedback described above. The smartphone 100 may also include a touch screen 120. A portion of the touch screen 120 is blown out to show a profile of the screen 120, which includes a transparent material 122. The transparent material 122 may be laid over sensors 124A-E. The sensors 124A-E may detect user input, such as force applied to the transparent material 122, as changes in capacitance at each of the sensors 124A-E. For example, a user pressing the screen 120 near sensor 124C would cause a change in capacitance 126B, 126C, and 126D in the screen 120 detectable by sensors 124B, 124C, and 124D, respectively. A processor within the smartphone 100 may detect the change in capacitances 126B, 126C, and 126D and correlate them with known x and y locations of the sensors 124B, 124C, and 124D to determine the user input location. The configuration of motor 110 and touch screen 120 separates the user input from the haptic feedback. Further, the haptic feedback is not correlated with the touch screen 120 in that haptic feedback cannot be delivered to particular locations of the touch screen 120.
Other conventional tactile sensing technologies include, for example, resistive or piezoresistive sensors that process input based on a resistance change as a function of the contact location and/or applied force. These resistive sensors consume significant amounts of power. They also can measure only one contact point and cannot detect the amount of force applied. Another conventional tactile sensing technology is a tunnel effect sensor that converts stress into modulated current density by means of the quantum tunneling effect. However they require a charge-couple device (CCD) camera, which is bulky and difficult to integrate into an electronic device. Yet another conventional tactile sensing technology is a capacitive sensor, which detects input based on a change of capacitance in a contact point. This technology provides static detection, but lacks the ability to quantify the amount of force or pressure applied. Yet other conventional tactile sensing technologies include ultrasonic-based sensors, optical sensors, and magnetism-based sensors. However, these sensors are all difficult to integrate into electronic devices because of weight and size issues.
Only some drawbacks to conventional electronic devices and input and output to those devices are described above. However these drawbacks illustrate a need for further improvements in user input and user feedback to improve capability of electronic devices, such as consumer smartphones, to interact with users.